Cheap 51% attack on PoW cryptocurrencies is based on economic incentives

Bitcoin is a great invention. It is the first cryptocurrency. Today, most of the human mind potential concentrated in the computers engineering industry. Bitcoin, by its nature caused significant portion of this enormous analytics capacity to be invested in understanding economics. This is one of the greatest values Bitcoin created so far.

As for a potential of Bitcoin to become a widespread cryptocurrency without conceptual changes(moving from PoW to PoS), it is at the least miserable.

There is a well known model of cheap 51% attack on PoW crypto currencies based on economic incentives, possibility of which have never been refuted and actual culmination of which can take place at any moment, even now.

In general, it is based on an assumption that miners are profit making entities and not interested in the network survival unless it gives them higher profit than other investment alternatives. The attacker needs to mine at a loss. In an interrelated cryptocurrency network one can't mine at a loss alone. If one loses money, everyone else loose money too, until some of the miners will abandon their miners, sell it and leave the business. At such point attacker can increase his miners pool and keep mining at a loss. Repeat until get 51% of a mining capacity, therefore control the network. All mined crypto coins can be sold immediately. This leaves the attacker with just the burden of mining at a loss, which is around 1/1000 of the market capitalization for a complete 51% attack. The end.

The future, if any, belongs to PoS crypto currencies such as Peercoin, Bitshares, Steem and Nxt and privately issued online currencies such as E-gold. While in current political state of the world undistributed currencies with single point of failure such as privately issued won't survive, they may become possible in some bright distant future.